An additive manufacturing process may include dispensing or extruding a feedstock material from a print head, or nozzle, that moves in three dimensions under computer control to manufacture a part. Depending on the properties of the feedstock material, its advancement through the print head may be difficult or result in undesirable effects. For example, when the feedstock material is or includes a glutinous material, the feedstock material may gum-up, clog, or otherwise foul the print head. As another example, when the feedstock material includes elongate carbon or other fibers, the fibers may kink, break, or otherwise buckle and become damaged or clog the print head. As yet another example, when the feedstock material is or includes an uncured or partially cured, curable resin, the resin may undesirably gradually cure inside the print head to progressively clog the print head and partially or completely obstruct the operative advancement of the feedstock material through the print head.